Study On Gas-liquid Mass Transfer Enhancement By Reactive Solid Particles

The intensification of chemical engineering process is an important way to realize the goal of the high process efficiency,less energy consumption and pollution emission,and it is also one of the important development directions of chemical engineering.In this paper,the enhancement of the gas-liquid mass transfer by using reactant particles in the liquid phase was studied experimentally and theoretically.The gas absorption enhanced by the sparingly soluble fine reactant particles in a reactor was analyzed theoretically.Based on the penetration theory,combining the cell model,a one-dimensional mass transfer model was developed and solved,by taking into the influences of the fine reactant particles' size and the particles' dissolution rate in liquid film account.The mathematical expressions of the mass transfer coefficient and the mass transfer enhancement factor were obtained.Furthermore,a two-dimensional interfacial mass transfer model was proposed by means of the mathematical statistics method and considering the location of particles and mutual interactions between particles,and its numerical solution was achieved by using the composite grid technology.The enhancement factor of the mass transfer increases with the solid holdup.However,it decreases with increasing the partial pressure of the gas solute,the particle size and the distance between particles and the gas-liquid interface.On the basis of the bubble column model,combining the two-dimensional interfacial mass transfer model,the gas-liquid-solid three-phase mass transfer with chemical reaction in a bubble column was solved numerically.The results show that the enhancement factor for the mass transfer increases with the increase of the solid holdup and the gas phase flow rate,but decreases with the increase of the partial pressure of the gas solute and the particle size.The two-phase mass transfer accompanied by an instantaneous irreversible chemical reaction in a bubble column was analyzed theoretically.A mass transfer model based on the surface-renewal model was developed and solved,which took into the effect of the turbulent and convective masstransfer account.The effects of the partial pressure of the gas solute,the gas-liquid flow rates,the gas-liquid interfacial concentration,the diffusion coefficients and the surface renewal rate on the mass transfer enhancement factor were investigated.The results show that the enhancement factor for the mass transfer increases with the increase of the concentration of the reactant in the liquid phase and the gas-phase flow rates,but decreases with the increase of the gas solute partial pressure.The absorption processes of SO₂ and CO₂ into Mg?OH?₂ slurry and Ca?OH?₂ slurry are separately studied experimentally in a reactor.The absorption processes of SO₂ separately into Mg?OH?₂ slurry,Ca?OH?₂ slurry and the NH₄HCO₃ aqueous solution are experimentally investigated in a bubble column.The experimental results were used to validate the mass transfer model,and the calculated values by present model agree well with the experimental results.